Antibiotic stewardship (i.e., promotion of appropriate antibiotics to improve outcomes, reduce antibiotic resistance, and decrease the spread of multidrug-resistant organisms) is an innovation increasingly viewed as urgent for the care of nursing home (NH) residents. Reasons underlying the call for antibiotic stewardship in NHs include an increasing prevalence of healthcare-associated infections with multidrug resistant organisms, high rates of use, and estimates suggesting 25%-75% of prescriptions may not be needed. Challenges to reducing potentially inappropriate antibiotic use are many, however, and relate to the NH structure, prescribing processes, and patient characteristics. The proposed implementation and dissemination project builds on published evidence and our research team's success implementing a randomized controlled trial in which we reduced antibiotic prescribing by 21.3% in experimental NHs compared to 6.7% in control NHs (p=0.031). Having demonstrated efficacy, our next step is broader implementation and dissemination, but doing so requires attention to several issues. For one thing, NH chains and their associated medical practices are administered separately, and it is unclear whether innovation implementation will be more effective if the organizational point of entry is primarily through the NH organization or through medical provider practices. Further, there is reason to understand the factors associated with implementation and outcomes for both points of entry, as some NHs do not have processes in place for quality improvement (meaning that entry through medical provider practices may be more effective), and others may have diverse physicians caring for their residents (meaning that entry though the NH organization may be more effective). Another issue involves which factors within the organization of a NH and/or its medical practices are associated with implementation effectiveness (fidelity) and innovation effectiveness (outcomes), and whether these vary depending on point of entry. The proposed project will address these issues by conducting an implementation trial with two arms based on different points of entry: NH chains or medical provider practices. Based on the results of this effort, we will promote regional and national dissemination, in collaboration with a Quality Improvement Organization (QIO) and other stakeholders. Therefore, our specific aims are: (1) In a 24-month antibiotic stewardship comparative (non-randomized) implementation study in 34 NHs, with two implementation arms (NH chain focus; medical practice focus), to identify elements of the implementation approach and organizational climate that are associated with (a) implementation effectiveness (i.e., uptake and fidelity) and (b) innovation effectiveness (i.e., prescribing and health outcomes); and (2) To disseminate the program regionally and nationally. The proposed project, conducted by a team with extensive experience in this field, in collaboration with strong partners, has the potential to have national impact on this critical and complex issue.